1. Field of the Invention
This invention relates to needles used by the medical and veterinary professions for the injection of fluids into the veins of human patients and animals.
2. Description of the Prior Art
Needles are utilized for a plurality of purposes in the medical field. The function, or purpose, for which the needle is employed is an important factor in its design. This is particularly true of needles used for long-term intravenous therapy. Most intravenous administration needles have a hub associated with the shaft of the needle which supports the needle and transmits fluids thereto. The needle is inserted into the vein by holding it initially in a position close to the skin and substantially parallel to the vein, it is then pushed forward, penetrating the skin and entering the lumen to reside within the vein. In contrast, intramuscular or hypodermic needles are used for administering relatively small quantities of fluid (usually quite dilute) into tissue. Hypodermic needles generally have a plunger to force out the medication and they are oriented at approximately 45.degree. to the skin surface for an injection.
Obviously, needles used for intravenal injections must be extremely sharp in order to penetrate tissue and vein walls. At the same time, they must have an opening in order to permit passage of fluid through the needle into the vein. It has always been a difficult problem to provide a sufficiently sharp point on intravenous needles while simultaneously providing openings of sufficient size to permit the administration of blood or other relatively thick fluids. The needles presently used for intravenous administration of fluids have cutting points, formed by a beveled end cut with an opening created at the junction of the beveled edge and the needle bore. Such needles slice or slit the skin and vein wall in order to effect entry. U.S. Pat. Nos. 3,064,648 and 3,099,988 to Bujan and Ginsburg, respectively, and the French Pat. No. 1,142,769 to Viala, disclose examples of such needles.
When bevel cut needles are used for the long-term administration of intravenous fluids, the movements of the patient's recipient extremity and the muscular contractions of the vein itself, often cause the point of the needle to penetrate the wall of the blood vessel from the inside out, depositing fluid into the tissues surrounding the vein involved rather than into its lumen. This causes swelling and pain. This is "infiltration", well-known in the medico-nursing professions, as a concommitant phase of intravenous therapy. When infiltration occurs, the needle must be removed and re-inserted at another site. Not infrequently, re-insertion is repeated several times a day for the same patient, resulting in repeated pain and discomfort; not to mention the extended period following treatment during which the swelling and pain may continue. The expenditure of the medico-nursing personnel's time and the cost of such repetitious re-starting of the therapy represent added expenses to hospital management, which are eventually charged as additional expenses to the patients receiving such therapy.
The intravenous needle of the present invention is designed to improve intravenous therapy by substantially eliminating infiltration and by minimizing local trauma and infection. As described hereinafter, this is achieved by use of a puncturing point as distinguished from a cutting tip, and by provision of a closed tip with a single fluid emission opening disposed a measured distance upstream thereof, as distinguished from an end opening. A number of prior art disclosures have touched in varying ways upon the charactertistics which have here been synergistically combined to achieve previously unattained results.
A tapering point is disclosed in U.S. Pat. No. 3,181,336 granted to Schofield. This needle permits the emission of fluids through a slit formed through and along the entire tip. The design permits cutting of the skin and vein, and carries surface debris into the vein during entry. Furthermore, the closeness of the slit opening to the needle tip permits fluid to flow into surrounding tissue when the vein is pierced from inside out.
The disclosure of U.S. Pat. No. 2,634,726 granted to Hanson, bears interesting similarities to the present invention. Its closed tip and single side opening would yield a degree of satisfactory infiltration-proof therapy if other defects were not present. However, the chisel-like bevel cut is imitated, though closed off, and this defeats the goal of a puncture entry as opposed to a cutting entry. This structure also is flawed by placement of the opening on the side of the needle that necessarily rests at the bottom of a vein, because the unsymmetrical point of the needle imposes a specific orientation during insertion.
Finally, one must note the deceptive similarity of structure exhibited between the present invention and several hypodermit needles. The disclosures of U.S. Pat. No. 2,862,495 to Gewecke, French Pat. No. 1,196,601 to Morgun, and German Pat. No. 446818 to Weyl are rather typical of this class of needle. All show emission openings removed from the tip and Morgun even notes the inherent cleanliness of having a solid point rather than an end opening. Nevertheless, each of these needles uses the conical or similar relatively blunt points characteristic and essential for hypodermic injections wherein the needle is used to withdraw fluid from a vial and inject it into tissue as contrasted with long-term intravenous administration into a vein. Such hypodermic needles must have the emission opening relatively near the point to function. As shown by Gewecke and Weyl, hypodermic injections are also more effective if several openings surround the needle at the same location. This too, is completely unsatisfactory for intravenous therapy.